Tic Tac Toe - Detecting win, lose, or draw

This is a tic tac toe generator. Computer vs. Computer only, a little different than the usual Player vs. Computer. I have most of my code written for this, but the issue I am having is sometimes when I generate the game, the whole board fills up and there will be a line of X's and a line of O's and it will come up as a tie. Sometimes there is two lines of X's or two lines of O's generated, and the game doesn't stop after the first line with 3 in a row...any insights? Thank you. ``` namespace TicTacToe { public partial class Form1 : Form { private Random rn = new Random(); const int SIZE = 9; char[] cell = new char[SIZE]; char firstPlayer = ' ', secondPlayer = ' '; private void button1_Click(object sender, EventArgs e) { //Clear the labels and starting values for (int i = 0; i < SIZE; i++) { cell[i] = ' '; } label10.Text = ""; //Pick X or O to go first switch (rn.Next(2)) { case 0: firstPlayer = 'O'; secondPlayer = 'X'; break; case 1: firstPlayer = 'X'; secondPlayer = 'O'; break; } //Get five non-repeating numbers from 0 to 8 int[] positions = new int[5]; positions[0] = rn.Next(9); for (int i = 1; i < 5; i++) { int temp = rn.Next(9); for (int j = 0; j < i; j++) { if (temp == positions[j]) { i--; break; } else { positions[i] = temp; } } } //Set each position found to have first players letter for (int i = 0; i < 5; i++) { cell[positions[i]] = firstPlayer; } for (int i = 0; i < SIZE; i++) { if (cell[i] != firstPlayer) { cell[i] = secondPlayer; } } //Place cell values into the labels label1.Text = cell[0].ToString(); label2.Text = cell[1].ToString(); label3.Text = cell[2].ToString(); label4.Text = cell[3].ToString(); label5.Text = cell[4].ToString(); label6.Text = cell[5].ToString(); label7.Text = cell[6].ToString(); label8.Text = cell[7].ToString(); label9.Text = cell[8].ToString(); //Check for a winner switch(checkWinner()) { case 'T' : label10.Text = "It's a tie!"; break; case 'O' : label10.Text = "O Wins!"; break; case 'X' : label10.Text = "X Wins!"; break; default: label10.Text = "This will never appear"; break; } } private char checkWinner() { //return either 'T' for tie, 'O' for O wins, and 'X' for X wins char winner = ' '; int winning_line = 0; //check for a row win if(cell[0].Equals(cell[1]) && cell[0].Equals(cell[2])) { winning_line++; winner = cell[0]; } if (cell[3].Equals(cell[4]) && cell[3].Equals(cell[5])) { winning_line++; winner = cell[3]; } if (cell[6].Equals(cell[7]) && cell[6].Equals(cell[8])) { winning_line++; winner = cell[6]; } //check for column wins if (cell[0].Equals(cell[3]) && cell[0].Equals(cell[6])) { winning_line++; winner = cell[0]; } if (cell[1].Equals(cell[4]) && cell[1].Equals(cell[7])) { winning_line++; winner = cell[1]; } if (cell[2].Equals(cell[5]) && cell[2].Equals(cell[8])) { winning_line++; winner = cell[2]; } //check for diagonal winner if (cell[0].Equals(cell[4]) && cell[0].Equals(cell[8])) { winning_line++; winner = cell[0]; } if (cell[2].Equals(cell[4]) && cell[2].Equals(cell[8])) { winning_line++; winner = cell[2]; } if (winning_line == 0 || winning_line > 1) winner = 'T'; return winner; } public int i { get; set; } } } ```